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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>CSS盒子模型</title>
    <link rel="stylesheet" href="css_four.css">
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<body>

    <h1>h1-块级盒子</h1>
    <p>p-块级盒子</p>
    <pre>pre-块级盒子</pre>
    <div>div-块级盒子</div>

    <span>span-内联盒子</span>
    <span>span-内联盒子</span>
    <a href="#">a-内联盒子</a>
    <b>b-内联盒子</b>
    <br>
    <div class="box_before"></div>
    <div class="box"></div>
    <div class="box_after"></div>

    <div class="box_outline">
        <div class="box_size">233<br>233<br>233<br>233<br>233<br>233<br>233<br></div>
    </div>

    <div class="box_outline">
        <div class="box_margin"><br></div>
        <div class="box_margin1"></div>
    </div>

    <div class="box_outline">
        <p>1</p>
        <p>2</p>
        <p>3</p>
        <p>4</p>
        <p>5</p>
    </div>


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